Question

我的数据库中有一些数据：

Item      date          qty
gum       2012-03-13    1
soap      2012-03-12    3
soap      2012-03-11    10
candy     2012-03-04    20
sugar     2012-03-01    2

我想如果我为soap选择数据，我会得到如下数据：

Item       date            qty
soap       2012-03-12      35 (counting all data until max(date) of soap)
           (even soap is have twice input but get the max(date))

我只是有一个问题：

SELECT Item,MAX(date) FROM list WHERE Item LIKE 'soap'

如何放COUNT(qty)，所以我会得到上面的结果？

Answer 1

看起来你的例子是错的。它应该导致33不在35，因为糖来自年2013。知道:)这是查询：

select item, max(date) MaxDate,
  (select sum(qty) from t t1
   where t1.date <= (select max(date) from t
                     where item = 'soap')
  ) as totalQty
from t t2
where item = 'soap'
group by item

或许，如果你不喜欢看两次'肥皂'，那么这也应该有效：

select item, max(date) MaxDate,
  (select sum(qty) from t t1
   where t1.date <= (select max(date) from t
                     where item = @item)
  ) as totalQty
from t t2, (select @item := 'soap') init
where item = @item
group by item

Answer 2

SELECT Item, MAX(date), SUM(qty) 
FROM list 
WHERE Item = 'soap'
GROUP BY Item

计算数据库中的数据，其中当前数据是最大日期

2 个答案: